Charles Fox, Cosmetics and Toiletries, Vol. 99, pages 41-54, March 1984, made the comment that "almost any cosmetic can be formulated as a cream or lotion".
Fox points out that skin moisturizing properties which enhance smoothness, suppleness and softness of the skin represent a primary property of cosmetic creams and lotions. There is a vast and diverse array of oils, moisturizers and emollients which are employed for this purpose, such as mineral oil, propylene glycol and silicones. Many materials are employed because they introduce diverse properties to the cosmetic formulation. Fatty alcohols serve as moisturizing agents and also provide emulsion stability viscosity control and consistency. One attribute that fatty alcohols are noted to provide is a "smooth finish on rubout" (See Fox, supra page 52). Fox notes that stearic acid is a moisturizer and it is used also to form a soap emulsion system. Fox demonstrates the wide array of components which one may introduce to a cosmetic lotion.
Almost all cosmetics will provide a degree of protection to the skin to which it is applied. The level of protection is dependent upon a number of factors:
1. The uniformity of the cosmetic as a film on the epidermal surface; PA1 2. The resistance of the film to attack by body liquids and perspiration; PA1 3. The volatility of the cosmetic; PA1 4. The resistance of the film to abrasive and frictional attack; and PA1 5. The resistance of the film to ultraviolet light. PA1 1. the ability to deposit the film from a stable liquid phase; PA1 2. the deposition of a uniform plasticized film on the surface of the skin which possesses PA1 1. the separate formation of oil and water phases, PA1 2. combining the oil phase containing a sunsceening agent with a water phase into either an oil in water emulsion or into a water in oil emulsion, PA1 3. providing PHEMA in solution in combination with a plasticizer therefor, PA1 4. providing the solution in an aqueous phase, PA1 5. providing an emulsifying agent in the desired oil in water emulsion as part of an aqueous phase which is either combined with the oil phase or to another of the aqueous phase which will ultimately be combined in forming the desired oil in water emulsion, and PA1 6. combining the various phases to make the oil in water emulsion. PA1 the ability to deposit the film from a stable liquid phase, PA1 the ability to deposit a uniform plasticized film on the surface of the skin characterized by
Sunscreening agents are typically applied from a cosmetic formulation that is designed to enhance the functionality of the agent. They are generally used in acrylic emulsions. R. S. Berger, et al., J. Soc. Cosmet. Chem., 29, pp. 641-649 (1978) describe the use of sunscreen agents such as octyl p-N,N-dimethylamino benzoate (PABA) and an ammonium acrylate/acrylate ester polymer (see the "Synopsis"). The authors state
"An acrylate film-forming polymer was selected as the primary filmformer for the sunscreen preparation. This polymer is skin-adherent and water-resistant. When dried on the skin, however, the film is easily removed with soap and water. An oil-in-water emulsion containing the acrylate polymer and octyl dimethyl PABA was prepared. Ammonium isostearate served as the primary emulsifier." (see page 642) PA0 "An acrylate film-forming polymer was selected which could be solubilized by forming the ammoniated salt in an anionic soap emulsion. When the sunscreen preparation dries on the skin, the ammonia evaporates, fixing the insoluble polymer to the skin. Due to this `fugitive amine` transformation, the film is insoluble in water and resistant to rub-off. It is easily removed, however, by washing with soap and water . . . " (see page 646)
A number of polymeric thermoplastic materials have been utilized for a variety of cosmetic applications. Many of these materials are water soluble or dispersible. Consequently, any lotion in which they are provided will typically lack in moisture resistance. Even though polymeric thermoplastics are large molecules, i.e., macromolecules, solubilization of a film containing these large molecules by moisture can remove them as rapidly from the treated surface as would a comparable cosmetic formulation made from lower molecular weight materials. This stems from the fact that the macromolecule is typically present in small quantities in the cosmetic resulting in a small quantity of the macromolecule deposited on the skin. The erosion of the macromolecule by the relatively large mass of moisture is sufficient to quickly wipe away the presence of the macromolecule from the skin surface.
It would be desirable to utilize macromolecules which are moisture resistant in sunscreening cosmetic preparations because they could provide a level of cosmetic permanency on the epidermal surface that would insure ultraviolet light protection under a variety of conditions. However, the use of moisture resistant macromolecules is quite difficult in this application. Frequently, such moisture resistant macromolecules have poor film forming properties when deposited as an extremely thin film on an epidermal surface and should they possess good or adequate film forming properties, they frequently lack the essential properties of a suitable cosmetic.
This can be appreciated by recognizing that in a typical oil in water cosmetic formulation in which the macromolecule is present as a minor quantity, it is difficult to formulate the macromolecule in such a way that it can be released from the emulsion on application as a uniform, easily applied film containing whatever plasticization required for the cosmetic application. For example, the plasticization aids may separate from the macromolecule on application because the emulsion is being broken by an alteration of the chemistry of the emulsion. In addition, there are a number of important properties required of such a macromolecular layer on skin. For example, it is typically necessary for a film to be sufficiently thin enough in epidermis treatment that the recipient does have adverse sensations resulting therefrom. The film should not be greasy, brittle, tacky, gummy or oily. The film should not be receptive to inks, dyes, oils or other materials to which the surface treated skin is in contact. For example, one would not wish to have a cosmetic treatment which dissolves news print, or itself be dissolved by sebaceous oils. Because macromolecules have the capacity of engendering high viscosities, their utilization should provide pore penetrability sufficient to achieve effective bonding to the skin yet provide a film possessed of moisture permeability.
The attributes required of an effective cosmetic material which possesses moisture resistant properties on an epidermal layer are difficult to achieve. The conversion of an effective moisture resistant thermoplastic film forming macromolecule into an effective cosmetic material requires
i. good tactility and flexibility; PA2 ii. resistance to inks, dyes, oils or other materials to which the surface treated skin is in contact or is generated by the body, such as sebaceous oils; PA2 iii. ready penetrability into the skins pores and a velvety smooth skin feel; PA2 iv. water resistant, non-gummy rubout characteristics; and PA2 v. moisture resistance combined with air and moisture permeability (breathability). PA2 i. an active and volatile solvent, PA2 ii. a lesser intermediately active and nonvolatile solvent and PA2 iii. a least active and nonvolatile solvent. PA2 good tactility and the pliancy of skin to provide a velvety smooth skin feel, PA2 freedom from greasiness and oiliness; PA2 ready penetrability into the skin pores, PA2 water resistant, non-gummy rubout characteristics, PA2 non-adhesive bonding to hair so as to avoid conforming hair to a particular shape, and PA2 moisture resistance combined with air and moisture permeability (breathability).
a. therefore free of greasiness, brittleness, tackiness, gumminess and oiliness;
Hydroxyethyl methacrylate homopolymer [poly(2-hydroxyethyl methacrylate)], referred to herein by the abbreviation "PHEMA," is a macromolecule.sup.1 which, broadly speaking, has the repeating unit formula- ##STR1## wherein each X is hydrogen or methyl and not more than one X is methyl. The most common characterization of PHEMA possesses X as hydrogen only. FNT 1. "Macromolecule," as used herein, embraces a polymeric structure composed of repeating mer units. A polymer is defined herein as a macromolecule larger than an oligomer, the latter being defined as a structure of up to about 15 repeating mer units.
Hydroxyethyl methacrylate homopolymer and copolymers have been described in a variety of patents for use in cosmetic applications. For example, Shepherd et al., U.S. Pat. No. 3,574,822, patented Apr. 13, 1971,.sup.2 describe the use of powdered PHEMA or solutions of PHEMA for a number of applications such as hair setting composition, flavoring release component, cosmetic emulsions, insect repellent, sunscreen lotion, aerosols, nail enamels, cleansing cream, vanishing foundation cream, hand cream, emollient cream, face powder, baby powder, and lipstick. This patent shows that PHEMA is normally a brittle material and sufficiently brittle that it can be used to set hair and act as a lacquer for nail covering. Example 17 of the patent addresses the plasticization of PHEMA by incorporating glycerol, sorbitol, diethylene glycol, dipropylene glycol, ethylene glycol, and/or propylene glycol as plasticizers. This resulted in a more flexible hair spray but even with such plasticization the polymer was stiff enough to hold the hair in tension. This demonstrated that such a polymer, applied to the skin, would cause an adverse sensation to the user reflected by the fact that the film on the skin would resist a skin mobility. FNT 2. Note the following related patents to Shepherd, et al.: U.S. Pat. Nos. 3,577,518; 3,681,089; 3,681,248; 3,697,643; and 3,914,405.
Abrahams, U.S. Pat. No. 3,963,685, Patented June 15, 1976, describes a process for making PHEMA. The patent talks in terms of a number of uses for PHEMA including those set forth in the aforementioned Shepherd, et al. patents.